Process of refining oils



' which, when mixed with the oil in the form Patented Sept. 11,1928.

UNITED STATES 1,684,159 PATENT oFF1c SIJ'ZBREN TIJ'LISTRA, OF MADISONCOUNTY, ILLINOIS, ASSIGNOR TO ROXANA PETRO- LEUM CORPORATION, ACORPORATION 01? VIRGINIA.

PROCESS OF REFINING OILS.

Ho Drawing.

This invention relates to a process of refining oils, and consists inthe novel procedure hereinafter disclosed.

As is knowng many of the cracked hydrocarbon oils have a high sulphurcontent. It has been the practice to apply to these oils the so-calleddoctor treatment, which consists in treating such oils with a solutionof lead oxide dissolved in a caustic soda solution under agitation, andthen adding free sulphur to precipitate out the lead sulphide. Thedisadvantage of such a treatment is that it is extremely diificult toadd only the required amount of free sulphur to carry out the reaction,and, at the same time, prevent the solution of sulphur in thehydrocarbon oil..

The disadvantage of a high sulphur content in the final product is fullyrecognized, inasmuch as it causes corrosion of the metal containers andpassages with which it essentially comes in contact when used as a motorfluid. It is the purpose of the present invention to control the sulphurcontent of the finished product in order to avoid an excess of freesulphur, or sulphur dissolved in the oils, by providing a method ofprecipitation of the lead compounds produced by the action of the doctortreatment of oil.

Another advantage of the present process is the provision of a method oftreatment which may be conducted as a continuous process, resulting inthe removal of the products of the doctor treatment and, at the sametime, produciug a doctor sweet final product. The process, brieflystated, consists in the usual step of treatin the oil with a solutionformed from a solution of lead oxide and a solution of caustic soda.This treatment removes certain of the sulphur compounds in the oil andalso converts certain other of'the sulphur compounds present to a formin which they are unobj ectionable and not detrimental to the finalproduct.

The product is then allowed to settle and the excess of the doctorsolution is drained OE and the product given a water wash.

It is then treated with a polysulphide, such, for instance, as apolysulphide of sodium of a water solution of suitable concentration,releases a suflicient amount of free sulphur only to carry out thenecessary chemical reaction to precipitate from the oil the lead comundsresulting from the doctor treatment 1n the form of lead sulphide and, atthe same Application filed December 6, 192a. Serial No. 153,044. A

time, to prevent an excess of free sulphur resulting in the oil andthereby imparting to the product a corrosive efl'ect.

The reason that the polysul hides of the alkaline earth metals contempated for use in the present process release only a sufficient amount ofsulphur to complete the precipitating action of the lead sulphide isthat the sulphur atoms contained in the polysulphide compounds areloosely bound. Therefore, these polypsulphides easily decompose intoelementary sulphur and a sulphide or polysulphides with a lower sulphurcontent.

For example, and by way of illustration of the chemical action involved,the following reversible reactions occur in relation to thepolysulphides of sodium, namely:

Na S Na,S +S Na S 1:1: Na s +8 It therefore follows that,- when thepolysulphides of the type contemplated, when mixed with a'doctor treatedoil in a water solution, the sulphur is freed in the form of a watersolution which reacts with the lead compounds dissolved in the oil,producing the same chemical reaction to precipitate the lead compoundsfrom the oil.

When the sulphur is freed in this manner from the water solution of thepolysulphide, only a small amount of sulphur is released, due to thedecomposition of the polysulphide. The amount of sulphur that isreleased is dependent upon the amounts .1 of polysulphides and ofsulphide present in the water solution for the reason that, in everyreversible reaction, there is a definite relation between theconcentrations in the solution of the products of the reaction.Furthermore, inasmuch, as sulphur is soluble in oil, some of the freesulphur present in the water solution will dissolve in' the oil. But theamount that is dissolved will be determined by the definite relationshipbetween the concentration of the sulphur 1n the water polysulphidesolution and the concentration of free sulphur in the oil, so that theamount remaining in the final product can be easily controlled andreduced to an amount that will not be detrimental by imparting acorrosive action to the finished product.

By selecting the proper degree of concentration of polysulphides in thewater solution and of the proper composition of the polysulphide, it ispossible to maintain a very low content of free sulphur in the oil. Thatis to say, the sulphur content entering into the solution with the oilcan be held to a point where it is only sufiicient to cause the desiredprecipitation of the lead compounds dissolved in the oil as the resultof the doctor treatment and, at the same time, sufliciently low so thatthe finished oil is noncorrosive. Likewise, if there is an excessiveamount of sulphur in oil, the addition of a water solution of sodiumsulphide or of a water solution of a polysulphide having a low sulphurcontent, the sulphur may be removed from the oil to an extent suflicientto make it non-corrosive by the conversion of the sulphide orpolysulphide to a polysulphide having a higher sulphur content. Thisessentially follows from the fact that the reactions exemplified aboveare reversible and that the free sulphur in excess readily enters intochemical combination with the sulphide or the lower content sulphurpoly- I sulphide. This reaction is facilitated by using a highertemperature, preferably about 200 degrees Fahrenheit.

As an example of the practice of the process, the following proceduremay be had:

The oil stock is first treated with the doctor solution, that is to say,lead oxide dissolved in caustic soda solution. The doctor treated oil isthen allowedto settle and the excess of the doctor solution is drawnoff. This is then followed by a water wash. The product is then treatedwith a polysulphide solution, the solution for this purpose comprisingpreferably sodium disulphide or trisulphide. The polysulphide solutionmay be added in excess, as the excess of the solution has no detrimentaleffect uponthe product. It may be added, therefore, by a continuousfeed. This step of the treatment is preferably carried out at atemperature from 80 to 90 degrees Fahrenheit andv the polysulphidesolution is preferably approximately 21. five percent degree ofconcentration; The product is then allowed to settle and the treated oilis decanted off. It is then washedwith water and is ready to be Itfollows, therefore, that the process greatly improves the method oftreatment of doctor treated oils, as the operation is facilitated bypermitting continuous feed of the polysulphide solution and theresulting product is greatly improved by reason of the fact that excesssulphur in solution in the oil is avoided. It will be understood thatthe specific mention of the polysulphides of sodium is merely by way ofexample, and that any of the polysulphides capable of decomposing intofree sulphur and a sulphide of lower content is contemplated.

It will also be understood that the specific mode of procedure outlinedis not essential,

but what I claim and desire to secure by Letters Patent is 2- I 1. Theprocess of treating oils which consists in adding thereto a doctorsolution and then adding to said treated oil a water solution of apolysulphide capable of releasing free sulphur for precipitating thelead compounds from the oil. I

2. The process of treating hydrocarbon oils which consists in subjectingthe oil to a treatment with an alkali metal plumbite in a watersolution, then extracting the plumbite solution from the oil, thentreating the oil with an alkali metal polysulphide, and then removingthe .polysulphide solution fromthe oil.

3. The step in the treatment of hydrocarbon oils containing leadcompounds which consists .in addingthereto a polysulphide salt in aWater solution, which salt is capable of releasing only sufiicientsulphur to precipitate the lead compounds and to prevent an excessamount of sulphur entering into solution in the oil. SIJBREN TIJMSTRA.-

